Axial bearings for centrifugal pumps typically have a first thrust ring and a second thrust ring. The first thrust ring rotates relative to the second thrust ring. Axial bearings may be lubricated by the pumped fluid (i.e. product lubricated). The first thrust ring is frequently made of plastic resin, while the second thrust ring is made of a ceramic material. The first thrust ring wears more rapidly than the second thrust ring because ceramic is harder than the plastic resin. The first thrust ring needs to be replaced regularly, but the exact replacement time is difficult to determine. Predicting the longevity of the first thrust ring and the axial bearing depends on factors such as impurities in the pumped fluid, the viscosity of the pumped fluid, and the operating point of the pump. Presently, pump operators and users rely on the time-consuming disassembly and inspection of the centrifugal pump to determine when the first thrust ring or the axial bearing needs replacement. Disassembly of centrifugal pumps may be disruptive to manufacturing processes if, for example, a redundant pump is not incorporated into the manufacturing process.
Some background art pumps add electrical sensors to the axial bearings to gauge replacement times for the thrust rings. However, the addition of electrical sensors frequently means the addition of a seal, a gasket, and/or sealant where the leads for the electrical sensors enter the housing. As a result, a centrifugal pump having an electrical sensor may be prone to leak where the leads enter the housing. Moreover, the electrical sensors may be incompatible with the caustic chemicals frequently pumped by the centrifugal pump. Electrical sensors may be oxidized, corroded, or otherwise rendered inoperable over time.
Therefore, a need exists for an axial bearing which is capable of providing an indication of the need for the axial bearing's replacement, without the foregoing disadvantages of fluid leakage or indicator failure.